If he's not standing still and didn't used to pull back all the time, it sounds a lot more like misbehaving instead of standing still.
about the worst thing you could do is what kim angel said she did with her horse cocoa:
Any time she would freak out, I quickly untied her and walked her around to calm her down.
thats a perfect reward for misbehaving. Even if your horse is frightened, unless he's in a dangerous location, or is likely to hurt himself badly/get tangled, you can often just let them pull.
The best thing to do is to find a good halter, one that wont break. and either a very
(those snaps break easy) or a strong rope, and tie your horse to something that absolutely wont budge, but make sure you use an emergency knot and can release him if he gets tangled.
Go about doing things as normal and if he starts to pull yell no/buzzer sound, whatever you do. If he stops then, great, if he doesn't, let him pull, untying him would be a reward for pulling. And don't worry, if he just pulls, even for a while, the worst thing he can do is make his head a little sore. He'll soon figure out that pulling gets him nowhere.[/i]